Brand Beckham has sold underpants, razors, fish fingers, designer fashion and the game of football around the world, and now it has also come to the aid of Burberry’s £1,500-a-go trenchcoats.

The venerable British fashion label has credited a Christmas advertising campaign fronted by Romeo Beckham, the 12-year-old son of Victoria and David, with boosting sales in the US, Europe and the Middle East – and helping to make up for falling sales in Hong Kong in the wake of the pro-democracy demonstrations.

Sales of Burberry coats, bags and fashion climbed 14% to just over £600m in the three months to the end of December. That was better than City retail analysts had expected and Burberry bosses said the adverts featuring Beckham junior had been a big success.

The four minute film featured Romeo and 50 dancers – all decked out in the label’s trademark trenchcoats – spinning umbrellas on a London-themed set at Elstree studios. It racked up 9m views on Youtube and trended on Twitter all day following the campaign’s launch. A 10% increase in sales of trenchcoats followed, with demand particularly strong in the US. That offset a fall in sales in Hong Kong, which usually accounts for 10% of Burberry’s global sales, as civil rights protestors camped out in the streets.

The big increase in sales of the company’s trenchcoats means it is now taking on new staff at the factory where they are made in Castleford, Yorkshire. It currently employs 750 people, a quarter more than two years ago.

The success of the campaign was good news for Burberry but also marks the expansion of the Beckham brand into the next generation.

His mother Victoria is a friend of Christopher Bailey, Burberry’s designer and chief executive. Bailey has previously said that they discussed using Romeo to front the brand for more than a year before the youngster stepped into the studio.

Victoria has also championed the brand. She was recently pictured in one of Burberry’s top-selling ponchos and joining Romeo and husband David at the London launch of the Christmas campaign. Bailey said Romeo was an “utter joy” to work with.

The designer told Youtube channel On Demand Entertainment after the first campaign: “He’s the sweetest, loveliest little chap. He loves clothes and fashion, he has an aesthetic point of view. He knows what he likes and he had a lot of fun.”

Simon Fuller, the former Spice Girls manager, reportedly negotiated a £45,000 fee for Romeo’s one day of work on the ad, which was shot by fashion photographer Mario Testino and directed by Bailey in the style of an old-school musical.

It was Burberry’s first-ever Christmas ad to appear on TV and was also shown in cinemas and across social media around the world. Images from the advert were then used in a billboard campaign.

The tie-up with the Beckhams is a typically smart move for Bailey. He has transformed the image of Burberry from a fusty, aging brand worn by middle-aged golfers or ripped off for the football terraces into a modern global empire. Harnessing the power of social media and digital technology, Bailey has linked Burberry to new trends, including British indie bands, personalised clothing and young British fashion faces such as Cara Delevigne.

David Alexander, a consultant at retail advisory firm Conlumino, said: “On the marketing front, Burberry remains one of the most innovative brands in retail.”

Burberry would not comment on whether Romeo will appear in any future campaigns, but the brand has a history of long-term relations with the stars of its ads, such as Kate Moss and Emma Watson, and Beckham the younger is widely expected to be back in a trenchcoat in future.